diff --git a/my/calendar/holidays.py b/my/calendar/holidays.py
index 567ddad..6fa3560 100644
--- a/my/calendar/holidays.py
+++ b/my/calendar/holidays.py
@@ -20,8 +20,8 @@ def _calendar():
     # TODO would be nice to do it dynamically depending on the past timezones...
     tz = LTZ._get_tz(datetime.now())
     assert tz is not None
-
-    code = zone_to_countrycode(tz.zone)
+    zone = tz.zone; assert zone is not None
+    code = zone_to_countrycode(zone)
     Cal = registry.get_calendars()[code]
     return Cal()
 
diff --git a/my/core/common.py b/my/core/common.py
index ee7533c..96ab44c 100644
--- a/my/core/common.py
+++ b/my/core/common.py
@@ -572,7 +572,7 @@ def test_guess_datetime() -> None:
 def is_namedtuple(thing: Any) -> bool:
     # basic check to see if this is namedtuple-like
     _asdict = getattr(thing, '_asdict', None)
-    return _asdict and callable(_asdict)
+    return (_asdict is not None) and callable(_asdict)
 
 
 def asdict(thing: Any) -> Json:
diff --git a/my/core/orgmode.py b/my/core/orgmode.py
index f869bdd..5894b23 100644
--- a/my/core/orgmode.py
+++ b/my/core/orgmode.py
@@ -45,7 +45,7 @@ class TypedTable(Table):
         if len(header) == 2:
             # TODO later interpret first line as types
             header = header[1:]
-        tt._blocks = [header, *blocks[1:]]
+        setattr(tt, '_blocks', [header, *blocks[1:]])
         return tt
 
     @property
diff --git a/my/time/tz/via_location.py b/my/time/tz/via_location.py
index 2d627ad..fe3cd69 100644
--- a/my/time/tz/via_location.py
+++ b/my/time/tz/via_location.py
@@ -67,7 +67,8 @@ def _iter_local_dates(start=0, stop=None) -> Iterator[DayWithZone]:
             warnings.append("local time goes backwards {ldt} ({tz}) < {pdt}")
             continue
         pdt = ldt
-        yield DayWithZone(day=ndate, zone=tz.zone)
+        z = tz.zone; assert z is not None
+        yield DayWithZone(day=ndate, zone=z)
 
 
 def most_common(l):